1. Field of the Invention
The present invention relates to a CDMA receiver in a CDMA mobile communication system and a correlator allocation control method, and more particularly to a CDMA receiver and a correlator allocation control method which are capable of increasing the accuracy with which to track a path.
2. Description of the Related Art
There have heretofore been known CDMA receivers comprising a finger assembly and a searcher which has a correlator group, an adder group, and a path controller for searching for high-level reception timings from added corrected values and determining a reception timing at which to receive a signal with the finger assembly.
FIG. 1 of the accompanying drawings illustrates an instance of correlator allocation in a conventional delay profile calculator. In FIG. 1, the number of correlators 71 allocated to one user is 4, and the maximum number M of subscribing users is 4. As shown in FIG. 1, the number of correlators allocated to one user is fixed according to the conventional correlator allocation process.
The term “user” refers to a communication circuit or a mobile terminal to be connected for wireless communications, and the term “number of users” refers to the number of communication circuits or mobile terminals.
Japanese laid-open patent publication No. 2001-94473 discloses a conventional synchronous supplementary search process wherein correlators are selected from a plurality of searcher groups and allocated to users. Japanese laid-open patent publication No. 2001-189680 reveals a despreading apparatus which allocates a number of fingers depending on a path to users.
However, the conventional correlator allocation process has suffered the following problems:
According to the conventional correlator allocation process, the number of correlators allocated to one user is fixed regardless of the number of subscribing users. The time for calculating a delay profile is proportional to the size of a cell radius. Therefore, the conventional correlator allocation process has a first problem in that if the number of subscribing users is small, i.e., even if there are excessive correlators, the accuracy with which to track a path is lowered as the cell radius increases.
The conventional correlator allocation process also has a second problem in that if the number of subscribing users is small and the correlator allocation process is modified to allocate all the remaining excessive correlators, then when many new users are activated at once, the synchronism among the new users is deteriorated.